The invention relates to driving tools to be used with percussive hand-held machines primarily of the type incorporating a machine housing with a cylinder therein and having holding means thereon for supporting the tool in front of said cylinder axially movably between an inner and an outer position thereof, and in which cylinder a reciprocating drive piston via a gas cushion repeatedly drives a hammer piston forward to impact on and to move back away from the tool disposed in the inner position thereof, whereas the hammer piston is adapted to perform an idle blow and come to halt when the tool is disposed in said outer position thereof.
In the above type of machines, inter alia in connection with their use in railroad spike driving, there can under unhappy circumstances occur foot injuries the instant the machine is brought to rest. If the operator namely happens to lift the machine so that the tool, in response to the last blow delivered by the machine, is caused to bounce against the rail or other workpiece or against the arresting lever for the tool, the tool will spring back into the machine and can be hit by a next undamped blow or start a new hammer blow, whereby injuries are risked or at least the arresting lever is subjected to undesirable load.
Spring loaded spike guiding sleeves have been previously used on tools for driving railroad spikes as seen from for example patent specifications U.S. Pat. No. 1,808,452 and U.S. Pat. No. 2,325,728. These relate, however, to compressor dependent machines of unrelated type and are constructionally unsuited to solve the problems met by the present invention. The same applies to the nail guiding sleeve and spring shown in patent specification U.S. Pat. No. 2,671,216.